Method for in situ retorting of oil shale employing artificial barriers



I M. LSLUSSER METHODFOR IN SITU RETORTING OFOIL SHALE EMPLOYINGARTIFICIAL BARRIERS 1 Filed Sept.- so, 1964 MANIFOLD SYSTEM MANIFOLDSYSTEM" ATTORNEY MARION L. sLusgz-rn INVENTOR.

BY M & BM

METHOD FORIN SI'IU RE'I'ORTING OI OIL SIIALE EMPLOYING ARTIFICIALBARRIERS Marlon L. Slusser, Arlington, Tex.,' assignor'to Mobil OilCorporation, a corporation of New York Filed Sept. 30, 1964, Ser. No.400,413, 1t) Claims. .(Cl. 166-49) ans'mAc'r on THE DISCLOSURE Thisspecification describes: A method for the in situ -re-' toning of asubterranean deposit of oil' shale to recover hydrocarbons, and in whichmethod, a barrier to fluid flows is placed about that portion of the oilshaleto be retorted. More particularly, via spaced wells, a fluid withamaterial to seal openings in the deposit is injected. The

' material maybe hydraulic cement. Then, a fluidfor temporarily sealingthe openings is introduced into that portion of the depositto beretorted; via the wells. This fluid may be a thixotropic clay in'wa'ter, e.g'.,-a drilling mud.- T here-r after, the openings in thatportion of the-deposit to be retorted are filled, via the wells, with afluid capable of excluding the priorly injected fluids. Thislastinjected fluid I may be water or air. Lastly, in situ retorting iscarried out apart injection and production wells at increased pressuresvided in a massive oil shale formation in communication withfracturesjboth natural and artificial. Approximately 9000- s.c.f.h. ofair was injected into one well-and 85 vvvolume percent of the air wasrecovered at a 7 p.s.i.g. back pressure at-thc other well'. increasingthe back pressure to 37 p.s.i.g. at the air-recovery well resulted in noair recovery as substantially all the injected-air easiest to thesurrounding oil shale. formation through interconnecting fractures. I

it is obvious from the foregoing that the majority of the fluids flowingthrough the oil-shale between injection and production wells must berecoverable; otherwise, the

shale oil produced by retorting' cannot be recovered in acceptablequantities. This is especially important where the wells through whichfluids in the oil shale are'recovered are necessarily operated atincreased pressures. in one aspect, operation of these wells at anincreased pressure becomes necessary to maintain a desired fluid injecinthe mentioned portion of the deposit wherein fluid flows I are containedby the establishedbarrier, and hydrocarbons.

are recovered from these fluidflows.

This inve'ntion'relates to amethod forithe situ retort-F:

ing of oil shale to produce hydrocarbons which are commonly termed shaleoil.

Distributed throughout the .world are massive forma tions of oil shaleproviding a tremendous reserve of the organic-material kerogen." Themagnitude of these formations is clearly displayed in some areas by oilshale outcrops hundreds of feet in vertical extent. The organic materialkerogenis convertible to shale oil by re'torting at. temperaturesusually in excess of 700 F. The produced shale oil includes liquid andgaseous hydrocarbonous fractivity into the oilshaie for proper retortingconditions. In

another aspect,-it becomes necessary to operate spaced so that therecovery or production well serves as a pressure sink to facilitatethe-recoveryof the produced shale oil.

This invention is directed, in an in situ-method for retorting'oilshale, toward the placing of a barrier to fluid flows about that portionotoil shale to be retorted. The

I placing of this barrier is obtained by procedural steps which areuncomplicated inlnature and employ readily obtainable materials.Furthermore, these procedural steps are compatible with the procedures,materials, and operational structures employed with'the known in situmethods for retorting oil shale. V

It is therefore an object. of the present invention to provide an insituretorting method for recoveringhydrocarbons from oil'shale whichovercomes the stated problems. Another object is to recover a majorportion of the fluids flowing between an injection and a production wellduring the retorting of oil shale, especially at superattions. it hasbeen proposed to retort in situ portions of, the oil'shale formations asone means for producing shale oil.

. For thisv purpose, spaced apart wells penetrating the portion to beretortedare provided. Through such wells is-- the desired retortingresult effected principally by the con trolled flow of fluids throughthe oil'shale.

Insitu retorting may be obtained by injecting between the spacedwellsfluids which apply to the oil shale by suitable mechanisms adequate heatfor converting the kerogen into shale oil..The heat providing fluids maybe;

combustible gases, combustion-supporting gases, and preheated ga'ses,and mixtures thereof.

For the most part, these retorting methods, tive operation, depend uponcontrollably flowing the heating fluids through the oil shale and movingthe resulting shale oil to a point convenient for its recovery. It isthis control of fluid movement in the in situ retorting of shale oilwhich provides severe problems to a successful employment of suchmethods. The problems reside in the oil shale formations being traversedby a network of fractures,- h'oth natural and artificial, whichfractures are in fluid communieation'with one another at least to somedegree. All fluid flows must take place through these fractures in theoil shale as it is retorted-Thus, it is apparent that the control offluid flows through the fractures beis very-diflicult. Further, the lossof fluids via these fracfor eifecmospheric pressure levels. Yet anotherobject is to prevent the undesired loss of fluids' flowing betweeninjection and producing .wclls, especiallyjat superatmospheric pressurelevels, exteriorly of the portionof the oil shale'being retorted. Afurther object of. the present invention is the limiting of fluid flowsin accordance with the preceding objects by employing the injection andproduction wells andiother means normally used in conventional in situretorting procedures for producing shale oil. These and other objectswill be apparent to those skilled in the art when read in conjunctionwith the accompanying detailed description, the appended claims, and theattached drawings.

In FIGURES l and 2 of the drawings, there is illus-' .trated, in avertical section taken. through the earth, a

portion of an oil shale formation provided with suitable structures bywhich the method of this invention may be practiced.

Referring particularly to FIGURES 1 and z of the vided for conveyingfluids between the earth's-surface l4 and the fractures oropenings intheinterior of the oil shale 13. Such means may take the form of wells 16and 17 spaced apart a suitable; distance within the oil shale 13, andeach extending to a' suitable depth into communit ures to areas of theoil shale outside that portion being retorted increases in magnitudewith every pressure increase in the fluids moving between the points.For examcation with openings in and beyond the portion of the oil shale13 to be retorted. Extending downwardly from the earth's surface 14 tonear the full depth of the wells 16 I and 17 are conduits 18 and 19,respectively. The conduits Patented July 18, 1967 ings 29.

18 and l9 arese cured within the'respective wells 16 and 17 bysurrounding cement 21 or other suitable sealing material. Connected tothe upper extremities of the conduits 18 and 19 are wellhcads 22 and 23,respectively. A manifold system 24 may be disposed at the earth'ssurface to provide for the flow of fluids between the earths surface 14and the openings in the interior of the oil shale 13.

The manifold system 24 may be of conventional design.

and its particular form is not important to the present invention. Thewellheads 22 and 23 are interconnected by 26 and 27,.respectively, tothe manifold work of interconnecting fractures, naturalorartiflcial,,t0',

provide the principal fluid-carrying channels in the oil shale 13. Achannel 28, formed of some of these fractures, provides the most directfluid communication between the wells 16 and 17. Also, the wells 16 and17 and the channel 28 are in fluid communication with otheropenings'extending outwardly into the surrounding oil shale formation11. More particularly, such openings are those in which occurs the lossof the flowing fluids through the channel 28 in the oil shale13 atincreased pressure above Any-means may be used for the injection of suchfluid.

Preferably, cementing plugs 31 and 32 are disposed in the wells 16 and17, respectively. The plugs 31' and 32 are then driven downwardly with apressurizing fluid applied from the manifold system-24 for displacingthe firstmcntioncd fluid fromthe conduits l8 and 19 in the wells l6 and17 in substantial quantities and pressures into-the thief openings- 29.A suitable driving fluid for driving the cementing plugs 31 and 32 isWCIlCT-xHOWCVCX', other'fluids may be used. If desired, the cementingplugs 31 and 32 may be moved downwardly in the wells concurrently orscparately'whilc holding substantially the same pressure above each ofsuch plugs. This'insures that substantially 'the same injection pressureis maintained in each ofthe wells 16 and 17. After the fluid hasbeendisplaced into the th'ef openings 29 and has undergone a desiredconversion to the scaling material, the cementing plugs 31 I and 32 'maybe removed from the conduits 18 and 19, re-

atrnos'pheric levels between the wells '16 and 17. For pur-" poses ofdescription, such openingsare referred to and designated'as thiefopenings 29, although the oil shale-13 is shown without a subtendedstratum, it will bc. apparent' that the oil shale-13 obviously restsuponsome support which need not be shown or described. Usually, a fluid canbe circulated without any great geological loss from the-manifold system24 through. the well .16

through the channel 28 to the well. 17 when operated at low backpressures. However, increasing the back pressurein the well 17 obviouslycauses increased-amounts of the injected fluid to be unrecoverably lostfrom the. channel 28 and the wells 16 and 17 into the thief open- In theillustrative embodiment of the method of this invention now tobedescribed, the thief openings 29 will be sealed to fluid flows toprevent the loss of fluids passing through the channel 28 in the oilshale 13 between the wells 16 and 17 while the channel 28 and the Wells16 and 17 will remain open to fluid flows. A first step of this methodis the injecting, into openings. of the oil shale 13, of a fluid capableof subsequently producing a material sealing such openings to fluidflow. Examples of such fluid are mixtures with water of hydraulic cementand of thixotropic clay, and mixtures thereof. Also. fluids eonvertibleto plastics, and'precipitatable metal salts can spectively, byany-suitable means.

' Another step is filling the channel 28 with a fluid capable ofexcluding the first injected fluid from such opening. Preferably. suchfluid used for filling the channel 28 is one incapable of subsequentlyproducing a material permanently sealing openings in the oil shale 13.For example, such fluid may be water, air, 'gel-type clays and water,and mixtures thereof. Preferably, this step of filling the channel 28 isdelayed until the first injected fluid begins to form thematerial'sealing the thief openings 29. Thereafter, the fluid capable ofexcluding the first injccted fluid is moved through-the wells 16 and 17and the channel 28 from the manifold system 24. This step is clearlydisplayed in FIGURE 2. This excluding fluid may be circulated at anysuitable pressure from the manifold system 24 through the surfaceconduit 26, the-well 16, through the channel 28, into' the well 17. andthence upwardly through the surface conduit 27 to return the firstinjected fluid tothe manifold system 24. Preferably, the circulatingpressure is not'greater than the injection pressure at which the firstinjected fluid was introduced into the openings in the oil shale 13.Thus-sealing material is not displaced from the thief' openings 29 bythe excluding fluid which preferentially will flow through the channel28 between the wells l6and l7. However.=where there is a tendency todisplace the sealing material from the thief openings 29 it is preferredto use a mixture of water and a thixotropic clay to form a gel as theexcluding fluid to maintain seals inthe thief openings 29. The

' I thief openings 29 in' any event remain sealed with a sealbe used.Other fluids can be used as will be apparent to those skilled inthe'art. The amount of pressure differential to be sealed against andthe in situ retorting conditions are substantially determinative of theactive ingredient composition of the injecting fluid. A gel-type clayand neat cement mixture with water has been found to he of utility formost purposes since the amount of cement can be varied to-produce sealsof various strengths.

More particularly. the fluid is injected into the wells 16 and 17 viathe manifold system 24 in suitable amounts filling the channel 28 andthe thief openings 29 at least in part. Preferably. sufficicnt of thefluid for sealing the thief openings 29 is injected until the injectionpressure is about that of the maximum operating pressure of the oilshale retorting procedure. As is obvious, injection of several batchesof this fluid capable of providing a material sealing openings in theoil shale 13 may be necessary to fill the thief openings 29 to a desiredextent. An interval is allowed before each subsequent injection topermit the priorly injected fluid to set. Also. in some cases it isfound to be of particular advantage to use increasing concentrations ofthe active sealing ingredients during injection of the fluid.

ing material. as can be seen in FIGURE 2.

Alternatively. the excluding fluid may be moved from the manifold.system 24 simultaneously through the surface conduits 26 and 27 todisplace the first injected fluid from the wells 16 and 17 and thechannel 28 into the thief openings 29. Although this practice will fillthe channel 28 with the fluid for excluding the first injected fluid,there .is some danger of reopening the thief openings 29 to fluid loss.On such happening, it may be necessary to repeat the previous step ifthe loss of fluids into the thief openings 29 is too great. If desired,the excluding fluid here also may be a mixture of water and thixotropicclay to form a gel for reasons previously discussed.

If desired. the fluid for filling the channel 28 and excluding the firstinjected fluid may be a slug of water followed by air or thecombustion-supporting gas to be used in the in situ combustionprocedure. Alternatively, the

' combustion-supporting gas may be passed through the channel 28 toclear it of the first injected fluid or to amount of the last injectedfluid that enters the Returning now to FIGURE 1, a second embodiment ofthe method of the present invention will be described. The structuralarrangement previously described with respect to the drawings may beutilized. In this embodiment 'This fluid is injected through the channel28 in that port'ion of the oil shale 13 residing between the wells 16and 17 .which portion is to be retorted. Thereafter, the channel 28 isfilled with afluid capable of excluding therefrom the fluidfor'producinga sealing material in thethief openings 29, and lastly,follows the'carrying out'of. the

- in situ retorting procedure in that portion of the oil shale13.between the wells 16 and 17.

, As onestep of this embodiment, a flui'd capable of subsequentlyproducing a material temporarily sealing openings in the oil shale 13 tofluid flows is injected from the earth's surface through the channel 28.'Anyfluid capable of producing this desired result may be used. Forexample, a fluid .containinga mixture of water with a thixotropichydrated clay has been found tobe of utility. Drilling muds formed ofbentonite and water are especially suitable for use. Preferably, thisfluid is injected through the channel 28 in the .same rnanner as thefirst injected fluid,fsu ch as, hydraulic cement,.was introduced intothe oil shale 13 in the first-described embodiment..Preferably, thisfluid is introduced under pressure conditions similar 'to those used forcarrying out the in situ retorting of the oil shale.

As another step,.a fluid capable of'subsequently producing a materialsealing openings in the oil shale 13 to fluid flows is injected into thethief openings 29-00mmunicating with the wells 16 and 17. This fluid maybe the same as that described for the first injected fiuidof the firstembodiment. A fluid found to be of utility consistsof a mixture withwater of substancessclected from the group consisting of thixotropichydrated clay, hy draulic cement, and mixtures thereof. Preferably, suchfluid is introduced under the same conditions as that fluid filling. thechannel 28. This arrangement ;reduces the chann'el 28.This fluid can-beinjected through the wells 16 suitable means, such as-was described forthe first in- 'jected fluid inthe first embodiment. Preferably, the.wells 16 and 17 are filled with'such'fluid and the fluid displaced fromthese wells by cementing plugs 31 and 32 driven downwardly by apressured fluid applied from the manition it will be apparent that thefluid producing the relatively permanent sealing material may. bedisplaced into an ultimate position by a fluid producing a temporarysealing material or one-incapable of producing a sealing. material, or acombination of both. In another aspect, a material producing a temporarysealing material may be used to fill the channel 28 in that portion'ofthe oil shale to be retorted sons to block entry of the fluidproducing the relatively permanent seal whichis-introduced into theopeningsin that'portion-of the oil shale not to be retorted.

Although the present invention has been described.

relative to only two spaced wells, it will be obvious to those skilledin the art that it may be applied to various patterns of wells toprovide circumferential seals about distinct portions ofthe oil shale 13to be retorted. Thus, by, this means, seals capable of, preventinglosses of the operational-fluids at the pressures required for-insiturctorting of theoil shale are formed by application'of the describedsteps. v

Of particular advantage in this'invention is the use of I fluids formingsealing materials in which water of hydration is essential in theforming of the sealing material. in such instances, as the in situretorting produces elevated'temperatures at such seals, the water ofhydration is-removed and the seals will fail. Inasmuch as suchsealingmaterial as hydraulic cement has a heatcondu'ctive coeflicient much likeoil shale, auniform advance of the retorting temperatures through theoil shale will produce uniform extensionsof the retorting procedure-fromone. portion of the oil shale-to'another by rupturing the surroundingseals or barriers. Thus, by application of the i described steps toadjacent portions of the oil shale, sucand 17 into the interconnectedthief openings '29 by any -cessive portions of the oil shale may beretorted with .con-

tinuous control of the fluid flows-by the limitations imposed throughseals placed in the oil shalebeyond each portion being retorted. s

Although the present method has been described specifically applied tooil shale formations forillustrm tive purposes, it can be used in othertypes of earthen deposits containing hydrocarbon materials through whichfluids mustflow in openings such as fractures and the like during insitu retorting procedures. One example is' the Athabasca tar sands.

From the foregoing it will be apparent that there has been provided amethod well suited for satisfying all of the stated objects of thisinvention. Variouszchanges and alterations may be made in the. stepsdescribed for this method by those skilled in the art without departingfrom the spirit of the invention. It is intended that such changes andalterations under these conditionsare to be included within the scope ofthe followingappended claims. I

fluids-Any suitable fluid may be used; For example,

water is of utility. For this purpose, the cementing plugs.

31 and 32 are removed from the conduits l8 and 19, respectively, by anysuitable means. Thereafter, such excluding fluid is passed through thewells 16 and 17 from the manifold system 24 to displace the residentfluids this fluid is circulated in the same manner as was described inthe second-stepof the first embodiment. Preferably, the fluid isintroduced to fill the channel 28 at somewhat less pressure than theinjection pressures of either of the other injected fluids. Thus, thethief openings 29 in communication with the channel 28 and the wells -16and 17 remain filled with a sealing material of one In either of thedescribed embodiments of this invenfrom the wells 16 and 17 and channel28. Preferably,

I claim:

- 1. In an in situ retorting method for recovering hydrocarbons from thesubterranean deposit through well means in fluid communicationat spacedlocations with openings in and beyond that portion of the deposit to beretorted, the improvement comprising the steps of:

(a) injecting from the earth's surface via the well means into openingsin the deposit a fluid containing hydraulic cementand water in amountssuiiicicnt to subsequently produce a material sealing openingscontaining the fluid-to fluid flows, s

(b) injecting water from the earths surface via the well means into theopenings in that portion of the deposit to be retorted to exclude thefirst-mentioned fluid therefrom, and

(c) carrying out in situ retorting with fluid flows limited to theportion of the deposit to be retorted and recoveringthe resultinghydrocarbons from these fluid flows. I

2. In the method of. claim 1, the improvement in step (b) of injectingair from the earth's surface via the well 3.' 1n the method of claim 2,the improvement of varyiitg the amounts of hydraulic cement and watercontained in the injected fluid during the carrying out of step (a).

4. Inan in situ retorting method for recovering hydrocarbons from asubterranean deposit through well means in fluid communication at spacedlocations with openings in and beyond that portion of the deposit to beretortcd,

the improvement comprising the steps of:

,(a) injecting from the earths surface via the well means a fluidcapable .of subsequently producing a material sealing openingscontaining the fluid to fluid flows into openings in the deposit otherthan in that portion to be retorted and a fluid capable of subse-.I,'-.= quently producing a material temporarily sealingl openingscontaining said fluid to fluid flows during the time the first-mentionedfluid produces said'material into openings in that portion of thedeposit to be retortcd,

(b) filling via the well means the openings in that portion of thedeposit to be retorted with a fluid capable of excluding the priorlyinjected fluids from such openings, and- (c) carrying out in situretorting with fluid flows limited to the-portion of the deposit to beretorted and recovering the resulting hydrocarbons from these fluidflows.

5. ,In an in, situ retorting method for recovering hydrocarbons from asubterranean depositthrough well means in fluid communication at spacedlocations with openings in and beyond that portion of the deposit to beretortcd, the improvement comprising the steps of:

(a) injecting from the earths surface. via the well means a fluidcapable of subsequently producing amaterial temporarily sealing openingscontaining the fluid to fluid flows into openings in that portion of thedeposit to be retortcd,

(b) injecting from the earths surface via the well means of excludingthe priorly injected fluids from such openings, and v (d) carryingout insitu retorting with fluid flows limited to the portion of the deposit tobe retorted and recovering the resulting hydrocarbons from these fluidflows. g

6. In the method of claim 5, the improvement in step (21') wherein thefluid contains water and a thixotropic hydrated clay and in step (b)wherein the fluid contains water with a substanceselected from the groupconsisting of .thixotropic hydrated clay and hydraulic cement, andmixtures thereof.

7. In an in situ retorting method for recovering hydro carbons from asubterranean deposit through well means. in fluid communication atspaced locations with openings in and beyond that portion of the depositto be retortcd, the improvement comprising the steps of:

(a) injecting from the earths surface via the well means a thixotropichydrated clay and water mixture into openings -in that portion of thedeposit to be refrom the group consisting of thixotropic hydrated clayand hydraulic cement, and mixtures thereof, into openings in the depositother than in that portion to be retortcd,

(c) filling via the well means the openings in that'por- 1 tion of thedeposit to be retorted with water'to exclude said mixtures producingsealing materials therefrom, and (d) carrying outin situ retorting withfluid flows limited to the portion ofthe deposit to be retorted andrecovering the resulting hydrocarbons from these fluid flows. v

8. In an in situ retorting method for rccovcring'hydrocarbons from asubterranean deposit through well means in fluid communication at spacedlocations with openings in and beyond that portion of the deposit'tobe'retorted,

the improvement comprising the steps of (a) injecting at a firstpressure, which pressure is about the greatest in magnitude to beemployed during retorting, from the earths surface via the well means afluid capable of subsequently producing a material temporarily sealingopenings containing the fluid to fluid flows into openings in thatportion of the oil shale to be retortcd,

(b) injecting at a second pressure not greater than the first pressurefrom the earths surface via the well means-a fluid capable ofsubsequently producing a material sealing openings containing saidfl'uidto fluid flows into openings in the deposit other than in thatportion to be retortcd, Y Y

(c) filling via the well means at a pressure loss than the secondpressure the openings in that portion of the deposit to be retorted witha fluid capable of flowing to exclude thefluids producing a sealingmaterial from such openings, and 1 a (d) carrying out in situ retortingwith fluid flows limited to the portion of the deposit to be retortedand recovering the resulting hydrocarbons from these 9. In the method ofclaim 8, the improvement in step (a) wherein the fluid containswater'and a thixotropic clay and in step (b) wherein thefluid containswater with a substance selected from the group consisting of thixotropicclay .and hydraulic cement, and mixtures thereof. i

10. In the method of claim 8, the improvement in step (b) wherein thefluid contains water with a substance selected from the group consistingof thixotropic clay and hydraulic cement, and mixtures thereof, and theamounts of each such substance in the fluid is varied during injectioninto the openings in the deposit.

References Cited, UNITED STATES PATENTS 1,870,869 8/1932 Ranney et a1299--2 2,365,039 12/1944 Andresen 166--29 2,973,813 3/1961 Parker 166-11 3,010,512 11/1961 Hurley et a1. 166-11 3,055,423 9/1962 Parker 166-113,070,159 12/1962 Marx 166-25 X 3,190,355 6/1965 Clement 166-25 X3,198,249 8/1965 Wiliman 16625 X CHARLES E. OCONNELL, Primary Examiner.

ERNEST R. PURSER, STEPHEN]. NOVOSAD,

Examiners.

1. IN AN IN SITU RETORTING METHOD FOR RECOVERING HYDROCARBONS FROM THESUBTERRANEAN DEPOSIT THROUGH WELL MEANS IN FLUID COMMUNICATION AT SPACEDLOCATIONS WITH OPENINGS IN AND BEYOND THAT PORTION OF THE DEPOSIT TO BERETORTED, THE IMPROVEMENT COMPRISING THE STEPS OF: (A) INJECTING FROMTHE EARTH''S SURFACE VIA THE WELL MEANS INTO OPENINGS IN THE DEPOSIT AFLUID CONTAINING HYDRAULIC CEMENT AND WATER IN AMOUNTS SUFFICIENT TOSUBSEQUENTLY PRODUCE A MATERIAL SEALING OPENINGS CONTAINING THE FLUID TOFLUID FLOWS, (B) INJECTING WATER FROM THE EARTH''S SURFACE VIA THE WELLMEANS INTO THE OPENINGS IN THAT PORTION OF THE DEPOSIT TO BE RETORTED TOEXCLUDE THE FIRST-MENTIONED FLUID THEREFROM, AND (C) CARRYING OUT INSITU RETORTING WITH FLUID FLOWS LIMITED TO THE PORTION OF THE DEPOSIT TOBE RETORTED AND RECOVERING THE RESULTING HYDROCARBONS FROM THESE FLUIDFLOWS.